// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef NET_SPDY_HPACK_ENCODER_H_
#define NET_SPDY_HPACK_ENCODER_H_

#include <stddef.h>

#include <map>
#include <string>
#include <utility>
#include <vector>

#include "base/macros.h"
#include "base/strings/string_piece.h"
#include "net/base/net_export.h"
#include "net/spdy/hpack/hpack_header_table.h"
#include "net/spdy/hpack/hpack_output_stream.h"
#include "net/spdy/spdy_protocol.h"

// An HpackEncoder encodes header sets as outlined in
// http://tools.ietf.org/html/rfc7541.

namespace net {

class HpackHuffmanTable;

namespace test {
    class HpackEncoderPeer;
} // namespace test

class NET_EXPORT_PRIVATE HpackEncoder {
public:
    friend class test::HpackEncoderPeer;

    // |table| is an initialized HPACK Huffman table, having an
    // externally-managed lifetime which spans beyond HpackEncoder.
    explicit HpackEncoder(const HpackHuffmanTable& table);
    ~HpackEncoder();

    // Encodes the given header set into the given string. Returns
    // whether or not the encoding was successful.
    bool EncodeHeaderSet(const SpdyHeaderBlock& header_set, std::string* output);

    // Encodes the given header set into the given string. Only non-indexed
    // literal representations are emitted, bypassing the header table. Huffman
    // coding is also not used. Returns whether the encoding was successful.
    bool EncodeHeaderSetWithoutCompression(const SpdyHeaderBlock& header_set,
        std::string* output);

    // Called upon a change to SETTINGS_HEADER_TABLE_SIZE. Specifically, this
    // is to be called after receiving (and sending an acknowledgement for) a
    // SETTINGS_HEADER_TABLE_SIZE update from the remote decoding endpoint.
    void ApplyHeaderTableSizeSetting(size_t size_setting);

    size_t CurrentHeaderTableSizeSetting() const
    {
        return header_table_.settings_size_bound();
    }

    void SetHeaderTableDebugVisitor(
        std::unique_ptr<HpackHeaderTable::DebugVisitorInterface> visitor)
    {
        header_table_.set_debug_visitor(std::move(visitor));
    }

private:
    typedef std::pair<base::StringPiece, base::StringPiece> Representation;
    typedef std::vector<Representation> Representations;

    // Emits a static/dynamic indexed representation (Section 7.1).
    void EmitIndex(const HpackEntry* entry);

    // Emits a literal representation (Section 7.2).
    void EmitIndexedLiteral(const Representation& representation);
    void EmitNonIndexedLiteral(const Representation& representation);
    void EmitLiteral(const Representation& representation);

    // Emits a Huffman or identity string (whichever is smaller).
    void EmitString(base::StringPiece str);

    // Emits the current dynamic table size if the table size was recently
    // updated and we have not yet emitted it (Section 6.3).
    void MaybeEmitTableSize();

    // Crumbles a cookie header into ";" delimited crumbs.
    static void CookieToCrumbs(const Representation& cookie,
        Representations* crumbs_out);

    // Crumbles other header field values at \0 delimiters.
    static void DecomposeRepresentation(const Representation& header_field,
        Representations* out);

    HpackHeaderTable header_table_;
    HpackOutputStream output_stream_;

    const HpackHuffmanTable& huffman_table_;
    size_t min_table_size_setting_received_;
    bool allow_huffman_compression_;
    bool should_emit_table_size_;

    DISALLOW_COPY_AND_ASSIGN(HpackEncoder);
};

} // namespace net

#endif // NET_SPDY_HPACK_ENCODER_H_
